Thats what my Friend gave me:
pHitEnt->pev->renderfx = kRenderFxGlowShell;
pHitEnt->pev->rendercolor = Vector(0, 255, 0);
He said, "pHitEnt" is an Entity from Type "CBaseEntity" and to add a holo effect you just have to use another constant, which is listet in the list of other constants.
I don't understand any word, but I hope that helps
Here is a List from the Basic glowing Colors that can be done:
Yellow:
255, 255, 0
Blue:
0, 0, 255
Red:
255, 0, 0
Green:
0, 255, 0
Purple:
255, 0, 255
Cyan:
0, 255, 255
White:
255, 255, 255
Black:
0,0,0
You can mix them of course, so if you do 255, 80, 0 you would have a dark/orange yellow!